The present invention relates to a new catalyst system and a process for using this catalyst for the conversion of short chained alcohols such as methanol to hydrocarbons. In particular, the present invention is directed to a new catalyst system used in a process of the conversion of methanol to lower unsaturated hydrocarbons in the C.sub.2 -C.sub.4 range.
The catalytic conversion of methanol to hydrocarbons is a well-known process. Many different catalysts have been described in the literature as effective in this process. For example, it has been demonstrated that zeolite-based catalysts, metal sulfates, metal phosphates, and heteropolyacids can be used as catalysts for the conversion of methanol to hydrocarbons.
Recently, industrial commitment to methanol conversion or upgrading has increased for a number of reasons, one of which is its availability from several different feedstocks. Moreover, heteropolyacid catalysts for use in methanol conversion have been attracting attention since they show activity even at temperatures as low as 300.degree. C. because of their strong acidity. In Japanese Patent Application No. 121,018, heteropolyacids are disclosed as being suitable for the conversion of short chained alcohols or oxygen containing compounds to hydrocarbons. The conditions for the reaction are from a temperature range of 250.degree.-400.degree. C. at a pressure of between ambient to 200 kg/cm.sup.2 g, and in the LHSV range of 0.1-10 hours.sup.-1.
The heteropolyacid described in this Japanese patent application includes many compounds which vary depending on the condensed coordination elements, the central elements and the condensation forms. The Japanese patent application specifically discloses that the hydrogen ions of the heteropolyacids are easily exchanged with other cations such as alkali metals including lithium, sodium, potassium, etc., nickel, cobalt, copper, manganese, lanthanide, silver, cesium, etc., to form the stable heteropolyacid salt. Moreover, the Japanese patent application discloses that these materials when applied to supports such as clay or zeolite, give improved conversion in the manufacture of the hydrocarbons.
Unfortunately, even the results achieved by the use of supported heteropolyacids/salts leave much to be desired. Accordingly, there is still significant room for improvement in the use of heteropolyacids/salts for the conversion of methanol to short-chained hydrocarbons. The present invention is directed to an improvement in the catalyst system used and the process for conversion of methanol to the short-chained hydrocarbons, and in particular, unsaturated short-chained hydrocarbons such as ethylene, propylene and butylene.